Catalysts suitable for dehydrogenation processes



by the dehydrogenation of alcohols.

Patented Apr. 18, 1950 CATALYSTS SUITABLEFOR' DEHYDEU-GENATION'PR'OCESSES" Ernest Charles and; Pierre: Robinet, Glamccy;

France, assignors. .to Societe: Normande' De Produits Chimiques, Paris,France, a -corppraetion of France No Drawing. Application September20,1948; se-

Claims. 1 This application relates tocatalysts suitable fordehydrogenation processes and is a continuation-impart of ourapplication Serial No. 728,200 filed 12th February, 1947, now abandoned;

It is well-known that-esters may be obtained In particular, thepossibility'of preparing methyl formate by-the dehydrogenation ofmethanol has been known since 1916 (Mannich and Gilmann, Berichte; 49;586) 1 and the equilibrium of this-reaction was' determ'ined' in 1926 byChristiansen (J2 Chem. Soc. 1926, 413). Up to the present time, however,this process has not proved industrially practicable since-the usualcatalysts,

such asthoseobtained by reduction of metallic oxidesand applied,generally, on a non-metallic support such as pumice orkieselguhr, havenot proved sufficientlyeffective. In this connection referencemay bemade to the publication L'a Catalyse en Chimie Organique (Catalysis inOrganic Chemistry) by Sabatier.

Thus, in the production of methylformate according-to the reaction:

com-on H-COO'CH; 2H,

ffacilitate secondary reactions and local overheating and thus shortenedthe life of the catalyst.

In recentyears attempts have been made to produce catalysts having ahighcoefficient of heat transmission so that the introduction of heat'or-its-abstraction, accordingly as the reaction involved may beexothermic orendothermic, is facilitated; Gfsuch catalysts perhaps the mostuseiulhave been those, of the Raney type and-these have proved successful forreactions in the liquid phase butare scarcely of practical value'forreactionsin the vapour phase. An improved" form of' catalysthasbeendeveloped by 'fischenko and'consists of aluminium alloy pelletswhichare activated lay-treatmentwith caustic soda; but unfortunately eventhis form of catalyst is not wholly satisfactory since-the: pellets rialNo. 50,236. In Canada February 11; 1947" create high charge losses inthe furnaces and veiy often cause premature clogging.

It is an object of the present inventionto'produce catalysts ofcavernous alloy: skeleton structure: which are of-- particular value intheconversion of alcohols to esters and particularly the conversion ofmethyl alcohol to methyl formate.

According to the present" invention a catalyst suitablefor thedehydrogenationofalcohols comprises acavernous skeletoncatalytic masscon;- sisting essentially of separateand hollow pieces of which thesmaller dimensions. are not less than 6 min, Iormedof-analuminium-copper alloy and thesuriace of. which is porous and consistslargely of active-copper.

The catalysts of this invention are.v distin? guished from those ofRaney and thoseof Dolgov (J. Gen. Chem. U. S. S. R. 6. 145.6,.(1936)) inthat these latter consists essentially. either of a powder or atmost of.very small grainstructure. The same difference existshetween thecatalysts of this invention and those of Tischenko (J. AppliedChem. U.S. S. R., 14.3,93-(1941) in .thatthe latter are formedas pelletsof 3.to4 mm. in diameter presenting a. smallpercentage oiactive copper.

The present invention further provides a process for the production ofthe aforesaid cavernous skeleton catalysts which comprises converting analuminium copper alloy into cavernous pieces of smaller dimensions notless than 6 mm. and treating the pieces with an agent which at.- tacksand dissolves away aluminium thus imparting to the pieces a poroussurface consisting largely of copper adherent to the alloy skeleton.Preferably the so-treated pieces are washed with water and then with analcohol-and are stored under alcohol. Where they are to be used for thedehydrogenation of methanol or other alcohol, it is convenient tousethat alcohol :for. the washing, and. preserving medium.

Thus, in general terms the productionof. the catalysts. of thisinvention maybe effected as follows. An; aiu-miniumscopper alloy, towhich other activating metals m y tic-added if. desired. ispreparedhybringing 100 partsrnf aluminium to red. heat; and introducing. intothefused :ma's's thus ohtainedrfrom 10 to 100 parts, preferably to?!) partsandoptimally about .60 parts; ,of copper; the 1 whole mess being.constantly agitated. Any desired additionaiactivating:metals' may beadded andwhen aliomosenous-fiuid?mass-isob, tained itris'poured'; in-athinstream. of substantially constant'sectiom'thmughan oriflcezpiercedin a refractory crucible onto the'suriaofiofzwater long as two months."

contained in a tank, the water being vigourously agitated, for exampleby means of a turbine.

The alloy is thus produced in the form of cavernous pieces and thoughthe size of the pieces may vary it is found that pieces of meandimensions about mm. are most useful for operating in catalytic tubes of40 mm. diameter.

The cavernous pieces thus obtained are We claim:

1. A catalyst suitable for the dehydrogenation of alcohols whichcomprises a cavernous skeleton catalytic mass consisting essentially ofseparate and hollow pieces of which the smaller dimensions are at least6 mm., formed of an aluminium-copper alloy and the surface of which isporous and consists largely of active copper.

plunged into a solution of caustic soda, caustic potash or otheralkaline agent which attacks aluminium for a time sufficient to dissolveout part at least of the aluminium from the surface of the pieces.Preferably the treatment is conducted so that the product contains from6 to 35 optimally 12 to 18%, of active copper mainly concentrated at thesurfaces of the pieces, such surfaces having a porous structure.

The pieces are then well washed with water and then with methanol or anyother alcohol with which the catalyst may be intended to be used, and isstored under the alcohol so that the freshly prepared surfaces are notexposed to risk of oxidation in the air.

The following example will serve to illustrate the invention but is notto be regarded as limiting it in any way.

Example 508 g. of cavernous alloy pieces are prepared by pouring intowater with strong agitation a molten alloy consisting of 100 parts ofaluminium and 60 parts of copper. These alloy pieces are placed in ametal basket and the whole immersed in 3 litres of caustic soda B.). Atthe end of about 20 minutes the gas liberated amounts to about litresand the temperature of the liquid has risen to about C. The evolution ofhydrogen is then accelerated and in order to prevent an evolutiongreater than a rate of about 450 litres per hour it is frequentlynecessary to withdraw the basket from the liquid for short intervals.The whole operation is usually completed in about minutes, thetemperature of the bath then being about 98 C. and the total volume ofhydrogen liberated being about the 144 litres required to produce acatalyst containing about 15% of active copper. The product is thenwashed with water and with methanol,

the yield being about 400 g.

The catalyst thus obtained is of especial value in the conversion ofmethanol to methyl formate in accordance with the method set forth inour co-pending application No. 50,237 filed on even date herewith andleads, as explained therein, to

reactions, it has a very long life and greater activity than thehitherto known catalysts and it has a high coeilicient of heattransmission, giving in thick layers lower'charge losses than the knowncatalysts and permitting a higher passage velocity of the alcoholvapours to be converted and in consequence a higher hourly production ofester. Finally it may be mentioned that in ordinary use the catalystmaintains its activity for at.

least 3 to 4 weeks and can then be revived by a simple treatment withcaustic soda followed by washing. If this is effected in the catalyticapparatus itself the catalyst remains active for as 2. A catalystsuitable for the dehydrogenation of alcohols which comprises a cavernousskeleton catalytic mass consisting essentially of separate and hollowpieces of which the smaller dimensions are at least 6 mm., formed of analuminium-copper alloy structure consisting essentially and hollowpieces of which the smaller dimensions are at least 6 mm., formed of analuminiumcopper alloy structure consisting essentially of parts ofaluminium and 60 parts of copper and the surface of which is porous andconsists largely of active copper.

5. A catalyst suitable for the dehydrogenation of alcohols whichcomprises a cavernous skeleton catalytic mass consisting essentially ofseparate and hollow pieces of which the smaller dimensions are at least6 mm., and the mean dimensions about 10 mm., formed of analuminiumcopper alloy structure composed of 100 parts of aluminium and50 to 70 parts of copper and the surface of which is porous and consistslargely of active copper, the proportion of active coppe in the catalystbeing about 12 to 18%.

6. A process for the production. of a catalyst suitable for thedehydrogenation of alcohols which comprises converting analuminium-copper alloy into cavernous pieces of smaller dimensions atleast 6 mm., and treating the pieces with an agent which attacks anddissolves aluminium, thus imparting to the pieces a porous surfaceconsisting largely of active copper adherent to the alloy skeleton.

7. A process for the production of a catalyst suitable for thedehydrogenation of alcohols which comprises converting analuminium-copper alloy composed essentially of 100 parts of aluminiumand 10 to 100 parts of copper into cavernous pieces of smallerdimensions at least 6 mm., and of mean dimensions about 10 mm., andtreating the pieces with an agent which attacks and dissolves aluminium,thus imparting to the pieces a porous surface consisting largely ofactive copper adherent to the alloy skeleton.

8. A process for the production of a catalyst suitable for thedehydrogenation of alcohols which comprises converting analuminium-copper alloy into cavernous pieces of smaller dimensions atleast 6 mm., and treating the pieces with caustic soda to dissolve awaysurface aluminium until the product contains from 6 to 35% of activecopper mainly concentrated at the surfaces of the pieces.

9. A process for the production of a catalyst suitable for thedehydrogenation of alcohols which comprises converting analuminium-copper alloy composed essentially of 100 parts of g:

aluminium and 10 to 100 parts of copper into cavernous pieces of smallerdimensions at least 6 mm., and treating the pieces with caustic soda ito dissolve away surface aluminium un'til thie Q product contains from 6to 35% of active'eop'per mainly concentrated at the surfaces of thepieces.

10. A process for the production of a catalyst f j suitable for thedehydrogenation of alcohols}- which comprises converting analuminium-copper, alloy composed essentially of 100 parts-of aluminiumand 50 to 70 parts of copper into cavernous pieces of smaller dimensionsat leasti 6 m m., and treating the pieces with caustic soda to dissolveaway surface aluminium until the product contains from 12 to 18% ofactive copper mainly concentrated at the surfaces of the pieces. ERNESTCHARLES.

PIERRE ROBINET.

REFERENCES CITED The following references are of reeord. in the file ofthis patent? UNITED STATES PATENTS Brenner et al May 4, 1948

1. A CATALYST SUITABLE FOR THE DEHYDROGENATION OF ALCOHOLS WHICHCOMPRISES A CAVERNOUS SKELETON CATALYTIC MASS CONSISTING ESSENTIALLY OFSEPARATE AND HOLLOW PIECES OF WHICH THE SMALLER DIMENSIONS ARE AT LEAST6 MM., FORMED OF AN ALUMINIUM-COPPER ALLOY AND THE SURFACE OF WHICH ISPOROUS AND CONSISTS LARGELY OF ACTIVE COPPER.